Python 2.7 emits a DeprecationWarning warning if callable() is called and python has the -3 option. callable() was removed in Python 3.0, but it was also added again in Python 3.2 (issue #10518).

$ ./python -bb -3 -Werror 
Python 2.7.2+ (2.7:7bfedb159e82, Jul  5 2011, 13:23:38) 
>>> callable(int)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
DeprecationWarning: callable() not supported in 3.x; use isinstance(x, collections.Callable)

I propose to drop the warning from Python 2.7. Use the six module if you would like to support Python 3.1, or use directly the following workaround in your code:

def callable(obj):
   return any("__call__" in klass.__dict__ for klass in type(obj).__mro__)

Attached patch removes the warning.

By the way, the six should be updated for Python 3.2: callable is a builtin again ;-)

What about this change instead:

-    if (PyErr_WarnPy3k("callable() not supported in 3.x; "
+    if (PyErr_WarnPy3k("callable() not supported in 3.1; "

New changeset 1f814faaf54d by Victor Stinner in branch '2.7':
Close #12501: Adjust callable() warning: callable() is only not supported in
http://hg.python.org/cpython/rev/1f814faaf54d

New changeset 62bd0553693f by Florent Xicluna in branch '2.7':
Issue #12501: merge the discordant NEWS entries.
http://hg.python.org/cpython/rev/62bd0553693f